1. Field of the Invention
The present invention relates to an automotive drive apparatus in which an electric motor-generator and auxiliary machines are linked to a crank shaft of an engine by means of a belt, and particularly relates to a quiet, highly reliable automotive drive apparatus that enables efficient rotational driving of an electric motor-generator and auxiliary machines.
2. Description of the Related Art
In recent years, reductions in automobile exhaust gas and CO2 have been in demand for purposes of global environmental protection. There is an urgent need for improvements in automobile fuel consumption in particular, since CO2 is discharged in proportion to automobile fuel consumption. Hybrid vehicles and idling-reduced vehicles are spreading as fuel consumption improving measures. Steady engine improvements have also been actively pursued, although their fuel consumption improving effects are limited.
In automobiles, an automotive alternator that supplies electric power to automotive electrical equipment, storage batteries, etc., is normally coupled by means of a belt directly to a crank pulley that is coupled directly to an output shaft of an engine. Auxiliary machines such as water pumps, air conditioners, power steering pumps, etc., are also coupled to the crank pulley by means of belts in a similar manner to the automotive alternator.
The automotive alternator and the auxiliary machines are coupled by means of the belts directly to the crank pulley that is coupled directly to the output shaft of the engine, which operates constantly, and it is extremely important to reduce losses in the rotations of these belts for improvements in automobile fuel consumption since these auxiliary machines constitute loads on the engine even when they are not operating.
In that regard, improving generating efficiency in the automotive alternator is of course important. However, since input for power generation is obtained from engine output, in other words from fuel, electric power management is required so as to generate required amounts of power when required, etc., in such a way that efficiency in the engine and the vehicle as a whole are improved, and not simply generating efficiency alone. In particular, effective use of “regeneration”, in which kinetic energy that would otherwise be wasted is recovered and used to generate power during braking, etc., is extremely important for fuel consumption improvements.
In addition, since the belts are rotated by the engine constantly, loss due to slippage and thermal radiation from the belts as engine torque is being transmitted to the automotive alternator and the auxiliary machines not only makes engine efficiency poor, but also has a large influence on noise and belt service life.
In order to solve these problems, generated voltage has been controlled by gradually increasing the field current in such a way that sudden increases in torque load are not imposed on the engine when large electric loads have been connected to the alternator (see Patent Literature 1, for example). Engine stalling, belt load increases, and belt slippage are thereby prevented.
One-way clutches have also been used in automotive alternators to block a rotational transmission pathway in one direction to try to suppress early damage to belts, noise due to slippage, etc., and to prolong durable service life (see Patent Literature 2, for example).
Patent Literature 1: Japanese Patent Publication No. HEI 5-52160 (Gazette)
Patent Literature 2: Japanese Patent Publication No. HEI 7-72585 (Gazette)
In the technique according to Patent Literature 1, engine burden is reduced by controlling the operation of the alternator itself so as to cooperate with the engine. However, the technique according to Patent Literature 1 did not take into consideration overall action of the belts including those of auxiliary machines, and although at least some loss in the rotation of the belts was reduced, the effects thereof were small. In addition, since field current, which has a large time constant, is controlled, there are limits to its responsiveness, making it difficult to operate the alternator so as to cooperate any more closely with the engine.
In the technique according to Patent Literature 2, since the rotational transmission pathway between the automotive alternator and the engine is interrupted completely by the one-way clutch sliding mechanically, belt loss reductions, slippage noise suppression, and prolongment of durable service life have been effected to a certain extent, but have not been satisfactory. In addition, since the pulley that has the one-way clutch mechanism also has a small diameter and is complex in construction, significant problems still remain in the durability of the one-way clutch mechanism pulley itself. Since the one-way clutch is a mechanism that slides mechanically, and an automotive alternator that has a one-way clutch pulley stops later than the engine due to inertia in its rotor when the engine goes from low speed to high speed, fan noise due to rotation of the rotor has been unpleasant for the driver and for people in a vicinity of the vehicle.
Thus, the techniques according to Patent Literature 1 and 2 have been invented with a view to effects of the alternator on the engine and the belts and have not taken into consideration improvements in efficiency of the engine and the vehicle as a whole including the auxiliary machines.